1. Field of the Invention
This invention relates to zener diodes and more specifically to zener diodes made by temperature gradient zone melting.
2. Description of the Prior Art
Heretofore, zener diodes have been made by diffusion processes or epitaxial growth techniques. The diffusion process employed inherently results in P-N junctions which may not be sharply defined and the diffused regions of conductivity do not have a uniform level of resistivity throughout the region. An epitaxial growth process inherently produces solid contaminants which degrade the electrical characteristics of the P-N junction although the region as grown will be substantially of a constant uniform level of resistivity throughout.
Zener diodes rated under eight volts have a temperature coefficient which is dependent on the operating current. One or more forwarded operating diodes are surface series connected to such a zener diode in order to provide temperature compensation. This type circuit arrangement is employed as a precision voltage reference in control system, digital voltmeters, frequency standards, precision power supplies and other high accuracy applications. However, the necessary physical connections of such a series circuit arrangement, if not substantially perfect are potential sources of high resistance contacts, inherent thermal problems, faulty connections and possibly a failure of the circuit.
An object of this invention is to provide a new and improved zener diode which overcomes the deficiencies of prior art zeners.
Another object of this invention is to provide new and improved circuit arrangements embodying one or more zener diodes.
A further object of this invention is to provide a new and improved process for making a zener diode.
A still further object of this invention is to provide a new and improved process for making electrical circuit arrangements embodying one or more zener diodes.
Other objects of this invention will, in part, be obvious and will, in part, appear hereinafter.